arm64: dts: amd/seattle: Move and simplify fixed clocks

arm64: dts: amd/seattle: Move and simplify fixed clocks

The fixed clocks are not part of "simple-bus", so move them out of the
bus to the top-level. In the process, use the preferred node names of
"clock-<freq>". There's also little reason to have multiple fixed
clocks at the same frequencies, so remove them keeping the labels
to minimize the change.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250306-dt-amd-fixes-v1-2-011c423ba99a@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>